Radiant signaling system



Sept. 14, 192

RADIANT SIGNALING SYSTEM Filed April 27, 1922 5 sheets-sheet 1 a INVENTUR B m M I ma ATTORNEY Sept. 14 1926.

E. s. PURINGTO'N RADIANT SIGNALING sys'rmx Filed April 27.- 1922 5 Sheets-Sheet 2 H15 ATTORNEY Sept." 14 1926.

E. S. PURINGTON RADIANT SIGNALING SYSTEM Filed April 27, 1922 sshms snet 5 INVENTOR ms 4170mm Sept. 14 1926.

- 1,599,586 E. s. PURIINGTON RADIANT SIGNALING SYSTEM v Filed April 27. 1922 5 sheets sheet 4 w I 1W r V I I I V ,igm

I lWE/VTOR W A I Sept. 14 1926.

E. S. PURINGTON RADIANT SIGNALING SYSTEM Filed April 27 s Sheets-Shee t .3 2 Him we: QEB $6 2st 3:38

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' NITED STATES ELLISON S. PURINGTON, OF CAMBRIDGE, MASSACHT SETTS, ASSIGNORTO JOHN HAYS HAMMOND, JR., ORGLOUCEBTER, MASSACHUSETTS.

RADIANT SIGNALING SYSTEM.

Application filed 4pm 27,

This invention relates to radiant signaling systems, and more particularly to such systems employing a lurality of frequencies.

Some of the ob ects of the presentinvention are to provide an improved signaling system;.to pr'evide an improved method of producing signaling currents for use in the .transmission'ofintelligence; to provide a method of wobbling the frequency of thev sion or for the transmission of other wave forms of frequency less than the fundamental radio, with an eificiency of power amplification substantially as great as obtained in the amplification of continuous or single frequency waves; to provide a system in which the reception of radiant waves may bemade responsive to variations in frequency; and to provide other objects, which will appeair hereinafter.

Referring to the drawings: F gure 1 shows electrical connections' of a transmitting system, n accordance with the present invention;

F igure2 shows a receiving system; Figure 3-shows a modified form of receiv ,ing system;

' Figure'i showsa modified form of transmitting system, and

Figure 5 shows curves of output current andbf the wave length of the radiated wave with different grid andplate voltages of an oscillating tube.

Referring to Fig. 1, one embodiment of my invention comprises a vacuum when having a filament 12, grid 13, and plate 14. The filament is heated by a battery 15; and a suitable 'devicesuch .as' a rheostat (not shown) maybe provided in series w'iththe battery 15 to regulate the filament current in a well known manner. Thus the negative terminal of the tube 11- becomesa hot oath; ode,- and the electrons-emitted therefrom pass to the plate 14, being controlled by the 1922. Serial No. 558,971.

potential of the grid 13 with respect to the hot cathode.

The circuit of the grid 13 includes a wind ing 20 of an inductive coupling 21, a grid battery 22, a potentiometer 23, and a connection to the hot cathode. Bridged around the potentiometer coils is a circuit including a blocking condenser 24 an adjustable fesistance 25, and a source 26 of alternating current of the desired frequency of wobble, as will be more fully set forth subsequently. Thus there is provided a so-called resistance coupling between the source 26 and the circuit of thegrid 13, but it is understood that any desired form of coupling, such as inductive or capacitative, may be employed, as will be readily understood by those skilled in the art.

The circuit of the plate 14 includes a winding 30 of the coil 21 shunted by a suitable condenser 34, a 'plate potential battery 31,

conductor 32, and, the middle or adjustable terminal of the potentiometer 23. A air of by-pass condensers 33, 33 are bridged across the respective end portions of the winding of the potentiometer, being connected to each other. and to the conductor 32. The voltage of the plate anode battery 31 is higher than that of either the grid,bat-

tery 22 or the filament I heating battery. Thus a regenerative or self-oscillatory circuit is provided, the pulsations in the circuit of the plate. 14 being successively reproduced in the circuit of the grid 13 by the inductive coupling formed by the windings 20,

34 selected, and

average or mean grid voltage and the aver-- age 'or mean plate voltage during a radio frequency cycle with respect to the hot cathode. With generator 26 not excited there will be a certain frequency produced in the oscillatory circuit 21,- 34 depending among other things on the voltage of batteries 22 and 31. With generator 26 operating, alternating voltages are thrown into the grid and "plate circuits of tube 11 superimposed upon the directcurrent voltages of. the". sources 22 and 31. The fre ueney is determined by.

the instantaneous vo tages impressed on'thc grid and plate circuits respectively due to tentiometer 23 is provided to determine the relative voltages applied to said rid and plate circuits due to generator 26. y. proper adjustment thereof and of rheostat 25, it is found that the generator 26 produces variations in the frequency of radio current in oscillatory circuit 21, 34, with substantially no variations in amplitude.

An output current produced by the regenerator is induced into a third winding 40 of the coil 21. This winding is included in the grid circuit of a high power amplifier 41 ofconventional type having a filament heating battery 42 and a plate potential battery 43. A switch 51 controls the grid circuit of the amplifier. When used to produce current in the antenna circuit the switch 51 is closed, and voltages corresponding to the frequencies produced in the oscillatory circuit 30, 34 are impressed on the grid of amplifier tube 41. The plate circuit of the amplifier 41 includes. a usual coil 45 whereby it is inductively coupled to the circuit of the antenna 46. It is understood that instead of transmitting the waves through the ether, the antenna and ground may be replaced by a pair of linewires for so-call'ed Wired wireless or guided wave operation. The electrical characteristics of the circuit of the antenna 46 should be such as to show no appreciable resonance effects in the range over which the frequency is wobbled.

In Fig. 5 there is illustrated graphically an example of voltage variations, and variations in amplitude and wave length obtained. The left hand portion of the figure shows the modulation characteristics of the system. The right hand portion shows the wobbling characteristics. If the voltages applied are periodically varied,'"the output current will be constant in amplitude while the wave length is wobbled as shown by the lines AOB respectively. In the particular case illustrated (in both figures) the grid voltage varies from 95 (at point A) with maximum opposition of the potential of source 26, to +20 (at point B) when the source 26 is aiding fully. The plate voltages are simultaneously varied between +160 and +210 respec tively. The right hand portion of the diagram indicates that the wave lengthvaries from 505 to 526 meters (i. e. frequencies of about 594,100 to 566,500). It is thus ap parent that variations in frequency are produced, periodically without appreciable variation in amplitude.

The process of reception involves the production of modulated wobbled' radio-frequency at the receiver, by having the radio receiver circuits tuned to one portion of the wobble frequencies, for example the high wave length end of the wobble. ceived energy may then be detected in the The resame manner as energy modulated at a secondary frequency equal to the frequency at which the transmitted energy-is wobbled.

The electric waves produced by the transmitting station of Fig. '1 may be received by receiving systems similar to those shown in Figures 2 and 3. One form of receiving circuit is shown in Figure 2 for use with the rate of wobbling at frequencies within the range of audibility, or which can have their existence made known without the use of beats. For receiving and detecting the incoming energy there is provided a usual coupling from the receiving antenna 61 and ground 62, or from a pair of line wires, a tuning condenser 63, and a detector comprising a three-element vacuum tube. The pulsations set up in the plate circuit of the tube 64 traverse one winding of a transformer 65 whereby the energy may be transmit-ted into the grid circuit of a usual threeelement vacuum tube 66 for amplification. A by-pass condenser 67 of fixed capacity is provided in shunt with one winding of the transformer 65, and an adjustable condenser 68 is in shunt with the other winding thereof for tuning purposes. The condenser 68 may be used when the wohbling frequency is sine wave to tune to the output of the detector. For reception of speech,however, the variable condenser 68 may be set at zero capacity, it being understood that a suitable transformer 65, appropriate to speech 'frequencies is employed. The plate circuit of the tube 66 may be carried to an indicating device 69, which may take the form of a telephone receiver of conventional type, or

the circuit may be carried through one or Figure 3 may be employed. In this circuit the same coupling 60, and tube 64 are used as in Figure 2. The right hand winding of the transformer 65 is connected in the circuit of the grid of a second detector tube. 7 5, there being in this same circuit a secondary winding of a transformer 76 whoseprimary is in the circuit of a local source of electric regeneration. The tube 77 has the usual filament connected with a filament heating battery 78. A transformer 79 is connected so that the oscillations in the plate circuit are reproduced in the circuit of the grid for continuous regeneration, the coil 79 pro-- viding an inductive j coupling between the plate circuit and the-{grid circuit,

.oscillations such as a tube 77 connected for -The plate circuit of the second tube 75 .comprises an inductive coupling 80 whereby the oscillations in the plate clrcuit are induced into the grid circuitof an amplifying tube 81. The tube 81 is provided with three elements in a conventional manner, the filament being heated by a suitable battery 82 and the potential of the plate anode being maintained positive with reference to the filament cathode by means of a suitable battery 82. Included in the circuit of the plate of the tube 81 is a suitable indicating device 83 which may take the form of a usual set up oscillations of the desired frequency.

An inductive coupling .129 connects the plate circui of the tube 127 with the circuit of the potentiometer 23. Thus the potential across the outside terminals of the potentiometer 23 varies in accordance with the oscillations produced by the source 126 just described, the adjustment of the resistance 25v determining the effective voltage produced by the source 26 across-the potentiometer terminals. Including in series with'the secondary winding of the coupling 129 is a suitable blocking condenser 24. Thus an alternating voltage producedin the secondary 129 is impressed winding of the couplin upon the outside termina s of the potentlometer 23, and the arrangement is such that'the ,variations in potential thereby produced affects the gridv and plate circuits of thetube 1 11 in such amanner that there will be substantially no variation in amplitude of the output current of the-tube. 11, although variations in frequency occur, as previously described.

In operation, assuming. a system employing the transmissionstatlon shown in Figure 1 and the receiving station shown in Figure 2,.the source 26 and other power started, and the apparatus adjus ed as described, and'switch 51' is closed. The tube 11 operates as an oscillator of relatively high frequency, producing currents in osclllatory circuit 30, 34 which are varied in frequency without change of amplitude. The cyclical rate of frequency variation, that is, the rate of occurrence of, for example, the peaks of highest frequency, is the same as the frequency of the current produced by the gen stator 26 and the extent of frequency variaurces are' tion is determined by the amount of voltage impressed by the generator upon the potentiometer 23. The rate of wobble may be, for example, 500 cycles per second, and the extent of wobble from a wavelength of 505 to 526- meters, which would cause the mean value ofthe wave length to be 515.5 meters. Voltage corresponding to this Current of wobbled frequency is impressed upon the grid of the amplifier tube 41 by means of the coupling 21, and the output voltage of the amplifier tube is impressed in turn upon the antenna 46 by. coupling 45. Because of the constancy of amplitude of voltages and currents of the tube 41, it may operate at much higher electrical efiiciency than if it were used to amplify currents which could be used to transmit tone by transmitter modulati on rather than transmitter frequency variation. The nature of the current in antenna 46 maybe-checked'by exploringwith.

a wave meter with a thermal indicator. The presence of two symmetrical humps, one at about 505 meters and the other at about 526 indicate that the transmitter is in proper adjustment. Keying for signaling may be ac complished by opening and closing the switch 51. It may be otherwise accomplished by inserting the'key in the lead from rheostat 25 to condenser 24, in which case the current in antenna 46 is changed from continuous wave to wobbledwave.

The radiant energy is impressed upon the recelvmg antenna 61 and impressed from across the secondary condenser 63, into thevgrid of the detecting tube 64 in the usual manner. The receiving circuits, however, are ad usted to sharp resonance, 1n contrast with I the transmitting antenna circuit of 1 Figure 1. Thesharpness may be obtained by use of receiving coils and condensers of sufficiently low decrement, or by useof regeneration inany'bf the well knownmanners. Thus a radio receiver is provided which responds only when the transmitter wave is in the right portion of its cycle of wobble. For example, if the tuning is at 526 meters with the transmitteroperating as above described, voltage will be impressed on the grid of the detector tube 64 once every cycle, constituting 'avoltage which is wobbled but also substantially completely modulated at a frequency of500 cycles per second. If however the-receiving circuit is ad usted to be responsive at 515.5 meters,

voltage will beimpressed on the rid of the tube 64 twice every cycle of wob 1e, consti-' tuting a voltage which is wobbled at 500 cycles per second but substantially completelymodulated at 1,000 cycles per second. By the operation of the detector 64, currents are produced in the plate circuit corresponding to the am litude variation of voltage upon the grid 0 the tube, and these are impressed by coupling 65 upon the oftube 66, re-

voltage impressed on the I the transmitter.

peated in the plate circuit and indicated by device 69 in the usual manner.

For use as a radio telephone=transmitter, the generator 26 may be replaced by a source of speech voltage, such as the output of a microphone circuit comprising a microphone, battery and modulation transformer arranged in a well known manner. Or in case the power output of a microphone circuit is insufiicient, a speech amplifier may be used before impressing the voltage on the potentiometer 23. It is understood that for radio telephony all keys or switches shown in the diagram will be closed, the message being sent by talking into the microphone. The rate of wobble and extent of wobble in this case correspond respectively to the pitches and intensity of the voice of the speaker. The receiving circuits are appropriately tuned so that the modulation pro duced locally by resonance and impressed upon the grid of the detector will reproduce without production of marked overtones the potentiometer of The system comprising the transmitting station of Figure 4 and the receiving station of Figure 3 operates in a similar manner, the operation of the oscillating tube 127 being obvious from the foregoing description. The receiving station of Figure 3 employs the beat system of reception, the tube 77 and inductive couplings 7679 comprising a socalled heterodyne. The signals may be transmitted by wobbling the frequency produced by the source 26 by varying the relative potentials ofthe grid and plate ofthe tube 127, in accordance with the message to be transmitted, and these signals produce variations in the beats in the circuit of the tube 75.

It is obvious that the transmitting station shown inFigure 1 may be employed in combination with the receiving station of Figure 3, or with any other suitable form of receiving station, and similarly the transmitting station of Figure 4 may be employed in combination with the receiving station of Figure 2, or with any other suitable rece'iving station.

It is well known that. tuned circuits of the general character of the circuits including the-condensers 6368 maybe tuned in resonance with" currents of predetermined freaccording to the frequency of the current,

being greatest at the frequency for which the circuit has been designed to be in resonance and dropping 0E on each side of the predetermined frequency. The, degree of intensity with deviations in frequencies from the .selected one is extremely great at points immediately adjacent to, the selected frequency and the curve then rounds off and gradually forms a gently sloping line.

By resonance curve is meant a curve of current intensity, drawn to show variations in frequency,-other factors being constant, such ,the curve is steepest produce greatlyv exaggerated changes in intensity or amplitude of current and the employment of this principle is one of the main features of the present invention. Thus by wobbling the frequency produced by the-tube 11 and em: ploying tuned circuits, including condensers 63-458 which are resonant to frequencies closely approximating the frequency produced by the oscillating tube 11, great changes in amplitude in the current in the indicating devices 69 -83 are obtained.

The construction illustrated and described herein is merely what I now consider to be the-preferred embodiment of my invention, and it is-therefore to be distinctly understood that I do not limit myself thereto as many changes may bemade in points of detail and other embodiments resorted to without deviating from the true spirit and scope of my invention as defined by the appended claims.-

Having thus described theinvention, what is claimed is: l. The method of producing radiant oscillatory energy which comprises. producing an oscillating current of substantially constant amplitude, automatically wobbling the fre-. quency of said current, and utillzmg said plitude.

. 2. The method of producing radiant oscil- I latory energy which comprises producing in the plate circuit of a vacuum .tube an oscillatory current of substantially constant amplitude, automatically wobbling the frequency of said current, utilizing said wob bled frequency current to produce radiantoscillations of substantially constant amplitude, and transmitting a message by modifying the condition of the current as being .wobbled or unwobbled.

3. The method of producing radiant oscillatory energy which comprises producing in the plate circuit of a vacuum tube an oscillatory current of substantially constant ainplitude, and wobbling the frequency of said current by varying proportionately the grid voltage and the plate voltage of the tube.

4. The method of producing radiant oscillatory energy which comprises producing in the plate circuit of a vacuum tube an osc1llatory current of substantially constant amplitude; and wobblin the frequency of said current by periodica y varying proportioncurrent of substantially constant amplitude,

ately the grid voltage and the plate voltage of the tube.

5. The method of transmitting intelligence which comprises producing an oscillating current of substantially constant amplitude, wobbling the frequency of said current, impressing the oscillating current upon the ether, and receiving the radiant energy.

upon a circuit tuned slightly out of resogence which comprises producing in the plate circuit of a vacuum tube an oscillatory wobbling the frequenc of said current by varying roportionate y the grid voltage and the p ate voltage of the tube, impressin the oscillating current upon the ether, an receiving the radiant energy .upon'a circuit tuned slightl out of resonance with at least some of the equencies employed.

8. The method of transmitting intelligence which comprises producing in the plate circuit of a vacuum tube an oscillatory current of substantially constant amplitude, wobbling the frequency of said current by periodically var mg proportionately the grid voltage an theplate voltage of the tube, impressingthe oscillating current upon the ether, andreceiving the radiant energy upon a circuit tuned slightly out of resonance with at least some of the frequencies employed.

-9. The gence-which comprises producing an oscilating currentof substantially constant amplitude, wobbling the frequency of said cur-- rent,impressing the oscillating'current upon the ether, receiving the radiant energy upon a circuit tuned slightly out of resonance with at least some ofthe frequencies employed,

producing at. the receiver current offre-' quency corressonding 'tothat' at which the rst mentione current is wobbled, and producing beats in. the receiving circuit between said last-mentioned current and a local source of oscillations."

i 1 diant energy. method of transmitting .intelliquencies emplo ed.

10. The method. of transmitting intelli gence which comprises producing in the plate circuit of a vacuum tube an oscillatory current of substantially constant amplitude, wobbling the frequency of said current, impressing the oscillating current upon the ether,-receiving the radiant energy upon a circuit tuned sli h at least some 0% o the frequencies emplo ed producing at the receiver currentof a equency bearing a definite relation to that at which the first-mentioned current is wobbled, and producing beats in the receiving circuit betweensaid last-mentioned current and a local source 0 f oscillations..

11. The method of transmitting intelligence which comprises producing in the plate circuit of a vacuum tube an oscillatory current of substantially constant amplitude, wobbling the frequency of said current by varying proportionately the id voltage and the plate voltage of the tu impress ing the oscillating current upon the ether, receivin the radiant energy upon a circuit tuned slightly out of resonance with at least some of the frequencies employed, and producing beats in the receiving circuit.

1 12. The method of transmitting intellitly out of resonance with.

gence which comprises producing in the plate circuit of a? vacuum tube anoscillatory current of substantially constant amplitude, wobbling the freqency of said current by periodically varymg proportionately the grid voltage and the plate voltage of the tube, impressing the oscillating current upon the ether, receiving the radiant energy upon a circuit tuned slightly out of reso nance with at least some of the frequencies employed, and producing beats in the re ceiving circuit.

13. The method of transmitting intelligence which comprises producing in'the plate circuit of a vacuum tube an oscillatory current of substantially constant amplitude,

.wobbling the freqency of said current by varying proportionately the grid voltage andthe. plate voltage of the tube, amplifyingsaid'current through a relatively high power tube, impressing the osc1llat1ng current upon the ether, and receiving the ra-.

14. The methodof. transmitting intelligence -which comprises producing in .the plate circuit of a vacuum tube an osclllatory current of substantially constant amplitude, wobbling the'ireqency of'said current by varying proportionately "the grid Voltage and the plate voltage 'of the tube simultaneously, impressing thej oscillating current upon the ether, and receiving the radiant energy 'upon a circuit tuned slightly out of p resonance with at least some of the fre- 15. The met 0d of 'transmitting intelligence which comprises producing in the by radiant energy comprising means for;

slightly out of resonance with at least some.

of the frequencies employed;

16. The method of transmitting intelligence which comprises producing in the plate circuit of a vacuum tube an oscillating current of substantially constant amplitude, wobbling the frequency of said current by periodically varying proportionately the grid voltage and the plate voltage of the tube simultaneously, amplifying said current through a relatively high power tube, impressing the oscillating current upon the ether, receiving the radiant energy upon a circuit tuned slightly out of resonance with at least some of the frequencies employed, and producing beats in the receiving circuit.

17. In a transmitting system for radiant energy, means for; producing oscillatory currents of constant amplitude, and means for varying the frequency of said currents, said last-mentioned means comprising, a source of alternating current.

18. A system of transmitting intelligence by radiant energy comprising means for producing an oscillating current of substantially constant amplitude, automatic means for wobbling the frequency of said current. without substantially varying its amplitude,

and means for utilizing said wobbled fre quency current to produce radiant oscilla-V tions. v

19. A system of transmitting intelligence producing an oscillating current of substan-' tially constant amplitude, and means for wobbling the frequency of said current between predeterminedlimits, said last-mentioned means comprising a source of alternating current.

"20. A system for transmitting intelligence by radiant energy comprising a vacuum tube having a grid and a plate circuit, means for producing in said plate circuit" an oscil latory current of substantially constant amplitude and means arranged externally of the plate circuit for varying the frequency, said last-mentioned means comprising a source of electrical energy.

21. A system of transmitting intelligence by radiant ener comprisin a vacuum tube having a gri" "and a plate clrcuit, means for producing in-said plate circuit an oscil latory current of substantially constant amlitude, electrically energized means directy connected with'both of said circuits, for wobbling the frequencyv of said current,

-'w1tnou t substantially varying its amplitude and means for utilizing said wobble frequency current to produce radiant oscillations.

22. A system of transmitting intelligence by radiant energy comprising a three-electrode vacuum tube, means operatively connected with a plurality of electrodes of said tube for causing the tube to emit an oscillating current of substantially constant amplitude and means for varying the frequency of said current, said last-mentioned means comprising a source of alternating current.

23. A system of transmitting intelligence by radiant energy comprising means for producing an oscillating current of substantially constant am litude and wobbling the frequency of sai current, means for impressing electro-magnetic waves produced by said.

current upon the ether, and means for transmitting a message by alternatively causing the transmitted waves to be wobbledand unwobbled. Y

24. A system of transmitting intelligence by'radiant energy comprising a three-electrode vacuum tube, means connected with the electrodes of said tube for causing it to produce an oscillatory current of substantially constant amplitude, means for wobbling the frequency of said current, comprislng a source of energy separate from those for causing the tube to produce oscillations and means for alternatively rendering said last-mentioned source of energy operative and inoperative on said tube.

25. A system of transmitting intelligence by radiant energy comprising a vacuumlatory current of substantially constant am-' plitude and for varying the frequency of said current by varying proportionately the grid voltage and the plate voltage of said tube, means for impressing electro-magnetic waves produced by said current upon the ether, and means for receiving the radiant energy comprising a circuit tuned slightly out of resonance with at least some of the frequencies employed.

26. A system of transmitting intelligence by radiant energy comprising a vacuum tube having a grid and a plate, means operatively connected with said grid and plate for producing an oscillating current of substantially constant amplitude and for varying the frequency of said current, means for amplifyin said current comprising a threeelectro e vacuum tube of relatively high power, means for impressing the electromagnetic waves produced by said current upon the ether, and means for receiving the radiant energy comprising a c1rcuit tuned slightly out of resonance of at least some of the frequencies employed.

27 A system of transmitting intelligence 'by radiant energy comprising a three-elecamplitude and periodically varying frequen cy, a vacuum tube of relatively hlgh power for amplifying, said current, means for 1m-' pressing the electro-magnetic waves produced by said amplified current upon the ether, and means for receiving radiant en.- ergy comprising a circuit tuned slightly out i of resonance with at least some of the frequencies employed.

28. A system of transmitting intelligence by radiant energy comprising a three-electrode Vacuum tube, means operatively connected with a plurality of electrodes of said tube for causing the production of an oscillatory current of substantially constant amplitude and periodically varying frequency, a vacuum tube of relatively high power for amplifying said current, means for im-. pressing the electro-magnetic waves produced by said amplified current upon the ether, means for receiving radiant energy comprising a circuit tuned slightly out of resonance with at least some of the frequencies employed, and means for producing beats in the receiving circuit.

29. A system for producing oscillatory energy, comprising means for producing an oscillating current of substantially constant amplitude, automatic, periodically-acting means for wobbling the, frequency of said current, means for transmitting oscillations derived from said current and also of substantially constant amplitude, .and means for alternatively rendering said wobbling means operative and inoperative to send a message.

30. A system for producing oscillatory energy, comprising means for producing m the plate circuit of a three electrode vacuum tube an oscillatory current of substantially constant amplitude, means directly connected with both the plate and grid circuits of the tube for wobbling the frequency of said current, and means for trans mittingg oscillation derived from said -cur-.

rent and also of substantially constant amplitud'e.

31. The method of producing oscillatory energy which comprises producing in the plate circuit of a vacuum tube art oscillatory current of substantially constant amplitude,

and wobbling the frequency ,of said current by causing a source of alternating current to vary proportionately the grid voltage and the plate voltage of the tube.

32. The method of operating a three electrode thermionic oscillator comprising a circuit connecting two of the electrodes which consists of producing in said circuit an oscillatory current of constant amplitude, and wobbling the frequency by varying proportionately the voltage of'two of the electrodes.

33. The method of producing radiant oscillatory energy which comprises producing in the'plate circuit of a vacuum tube an os- "cillatory current, wobbling the frequency of said current while maintaining its amplitude constant by periodically varying proportionately the grid voltage and the plate voltage of the tube simultaneously.

34. The method of transmittingfintelhgence which comprises producing in the plate circuit of a vacuum tube an oscillatory current, wobbling the frequency of said current at a rate equivalent to the superaudible frequency while, maintaining the amplitude of the current substantially constant.

In testimony whereof I hereunto afiix my signature.

ELLISON S. PURINGTON. 

